Need some clarrification about efficient progress

[Doomboltz]

Greetings.
I had a question about research progress and the extra 10 percent research bonus that you get from using certain vehicles in the tech tree.

In this case, my question is about the Su-25. On the stat card it says "Efficient progress from IL-28 = 110%, as shown in the screenshot. My question is, is the efficient progress ONLY from the vanila IL-28, or do I also get similar efficient progress by using IL-28Sh, considering they’re in the same techtree group?

I just wanna make sure, because my IL-28Sh is spaded and the vanila one isn’t, and I wanna know if I can use my IL-28Sh to grind the Su-25 instead of spading the vanila one.

[Measured]

It’s just the vanilla IL-28 that will give the efficient progress bonus.

But, if you spade that one to research the Su-25, at least you’ll get the modification tier additional bonuses along the way (the ones you get when researching all mods within a tier) which will also help speed up the research of the Su-25.

[Doomboltz]

Thanks for the response ^^

[Berserker0011]

But it’s also not like that 10% extra does a lot in most cases. Especially not if you’re using a plane with poor performance to get it over something you can generally do better in